Dummynet is a FreeBSD system facility that
simulates network delay and loss by manipulating the IP queue inside the kernel.
Dummynet makes use
of " ipfw" which supports various types of IP filters for system network interfaces. The general idea is to create a "pipe" object and configure
it with the desired delay and loss parameters. The pipe gets added to a list of filtering "rules" which are used by dummynet to modify the
treatment of IP packets in desired ways.
Dummy net simulates the effect of
bounded size queues
Pipes are fixed-bandwidth channels. Queues represent queues of packets, associated with a weight, which share the bandwidth of the pipe they are connected to proportionally to their weight. These rules are numbered from 1 to 65535 and they are processed in the order that they are listed.
A Simple Tutorial on Dummy net
A FreeBsd implementation of dummynet is available from the author at Dummynet home.
Dummynet: A simple approach to the evaluation of network protocols.